Polarised relays



lDec. 24, 1957-u w. DE FLIGU ETVAL POLARISED RELAYS Filed July 6, 195s A I. Il lllllllR- l von each side of its pivotal axis.

POLARISED -RELAYS Wladimir'de Fligu and Paul L. Lavalle, Paris, France Application July 6, 1953,'Seral No. 366,302

Claims priority, application France March 23, 1953 4 Claims. (Cl. 317-172) Polarised relays are relays the operation of which depends on the direction of the energizing current, these relays do not respond, at least to a certain extent in the case of the usual types of relay, to a current owing in one direction and are only actuated by a current tiowing in the opposite direction.

Polarised relays are already known in which the polarisation is obtained by means of a permanent magnet which co-operates with the energizing winding of the relay.

The object of the present invention is to provide an electro-magnetic relay of the above type, in which the armature is urged in both directions, on the one hand by a permanent magnet co-operating with the energizing winding and, on the other hand, by a second permanent magnet which provides the return force.

The armature is thus subjected by these permanent magnets to two forces acting in opposition and the change of position of the armature is obtained by energisation of the winding whereby one of these forces prevails over the other. As soon as this state is altered, even very slowly, the armature moves very rapidly from one position to the other, since the action of the magnetic force which has become the greater, increases very rapidly whilst the magnetic force which opposes the first decreases, also very rapidly. The movement of the armature is thus extremely rapid both in the direction of closure and the direction of opening.

The permanent polarisation magnet may be connected in shunt to a part of the magnetic circuit of the relay, and preferably to a part of its yoke, for example, the core; the permanent return magnet may be secured to the yoke of the relay whilst at the same time it remains practically independent of the magnetic circuit of the latter.

In accordance with one form of embodiment of the invention, the moving armature is pivotally mounted on the yoke, the pivotal axis being constituted by a sharp edge of the latter, the arrangement being such that the permanent polarising magnet and the permanent return magnet are arranged on the same side of the armature This armature can conveniently be balanced about its pivotal axis, for example by means of a counter-weight which may be constituted simply by an extension of this armature.

The description which follows below with respect to the attached drawings (which have been given by way of example only and not in any sense by way of limitation) will make it quite clear how the invention may be carried into effect, the special features which are referred to, either in the drawings or in the text, forming of course a part of the said invention.

Figs. l and 2 are respectively side and front views in elevation of a polarised relay in accordance with the invention.

Fig. 3 is a partial View in perspective of the same.

In the drawings, 1 indicates a U-shaped yoke forming part of the magnetic circuit of the relay having an armature 2 provided, close to one of its ends, with contact nited States Patent studs 2a, 2b, and terminating, at its other end, in a curved-back portion 2c, which forms a balancing counterweight for the armature. The yoke 1 carries a central core 3 having a threaded extension 3a which is connected to the body of this core by a frustoconical bearing portion 3b which is housed in a central hole 1a also frustoconical, through the base of the U-shaped yoke; the assembly is secured by a nut 3c screwed on the threaded portion 3a.

The core 3 is connected magnetically, through polepieces 4 and 5, to the ends of a magnetic rod 6 in which there is inserted a spacer 7 of nonmagnetic material. The core 3 carries the energizing winding 8; it is provided at its free end with a pole-shoe 3d. The armature 2 is, in addition, subjected to a permanent magnet 9, which provides a return force and which is laterally secured to a branch of the yoke 1 just underneath the curved-back portion 2c of the armature. The latter pivots on an edge of this branch, the connection to the hinge being effected by a spring blade 12. 10 and 11 are contacts which are preferably mounted on screws provided with a micrometer adjustment and which cooperate with the contact studs 2a and 2b. The magnetic circuit is preferably made of pure iron or alloys which have been suitably treated and which have a high permeability and a low remanence, the polarising magnet 6 having a high coercive force.

In the relay which has just been described, the core 3 constitutes a magnetic shunt to the permanent magnet 6. The magnetic field of this magnet 6 is furthermore closed by the pole-pieces 4 and 5, the armature 2 and the U-shaped yoke 1.

The magnetic induction of this magnet thus divides between these two circuits. The function of the winding 8 is to modify the apparent permeability of the circuit including the core 3, so as to cause the part of the flux of the magnet 6 to vary, which passes through the armature 2 and the core 1 3, and thereby to vary the attraction which this core exerts on the armature.

When the direction of the current through the winding 8 is such that the direction of the tlux produced in the core 3 is the same as that of the ux produced by the magnet 6, the apparent permeability of this core isincreased and, consequently, the ux which passes by preference through the core 3 causes the force of attraction on the armature 2 to diminish.

Conversely, if the flux induced by the winding opposes 'hat of the permanent magnet, the apparent reluctance of the core 3 increases and a greater portion of the liux of the permanent magnet passes through the core 1-3 and the armature 2, so as to increase the force of attraction.

This relay may thus operate in several different ways in accordance with the relative dimensions of the permanent magnets 6 and 9 or of their action, the tendency to close being, of course, increased when the current passes through the winding 8 and creates in the core 3 a tiux which is opposed to that of the magnet 6, while the tendency to open is increased when these two iluxes are additive.

In particular, the magnet 6 may be powerful enough for its action to predominate over that of the magnet 9, in the absence of any current in the winding 8. The relay is thus normally closed and it can only be opened by the action of a current through the winding 8 which gives rise to an additive ux in the core 3. Currents in the opposite direction, no matter how powerful they may be, only result in an increase in the attraction of the'armature which has already closed.

Conversely, the magnet 9 may be predominant and, in the absence of current, the armature is released. A current which has such a direction as to cause an additive tiux in the core 3, cannot have any action on this armature no matter how strong it may be. On the other hand, a current in the opposite direction will result in the attraction of the armature.

Finally, in a third method of operation of the relay, each of the two magnets exerts a predominant action on the armature depending on the position of this latter, the armature thus remaning in the position which it occupies at the moment of interruption of the energizing current which has caused its displacement. In order to bring the armature into its other position, it is necessary either to apply a mechanical force to it or to pass a current in the opposite direction through the winding 8. In this way, if the armature is closed, the opening action may be obtained by means of a current which causes an additive flux in the core 3 and, conversely, if the armature is open, its closure can be caused by passing a current which gives rise to a flux in opposition.

ln this third case therefore, the relay operates in a different way depending on the direction of the energizing current; it behaves in a way, like a polarised relay having two positions of stability.

In practice, these three types of operation, which allow most of the problems presented by polarised relays to be solved, may be obtained with a relay having the same characteristics, comprising a magnet 6 having an excess of magneto-active force, by simply varying the thickness or the nature of the spacer 7. A packing piece '7 of low reluctance will correspond to the first type of operation (the relay normally closed, the opening being controlled); a spacer of higher reluctance corresponds to the third type of operation (both opening and closure controlled); and finally a spacer of still higher reluctance corresponds to the second type of operation (the relay being normally open, its closure being controlled).

In any event, the reluctance of the spacer 7 is high with respect to the parasitic air-gaps, such as those which exist in the joint areas of the various elements which make up the magnetic circuit, however close may be the mechanical contact between these elements; the relatively high reluctance of the spacer '7 allows neglecting these air-gaps or rather prevents them from influencing the operation of the relay by their small random variations. In addition, the reluctance of the spacer 7 prevents the magnet 6 from being inliuenced by the magnetisation of the core 3, no matter whether this magnetisation takes place in one direction or the other.

Thus any excess currents applied to the relay, which have no influence on its operation, have also no effect on the state of magnetisation of the magnet 6 and therefore have no effect on the accuracy of the point of operation of the relay.

To this end, furthermore, the cross-section of the core 2, taking account of the magnetic permeability of the metal or the alloy of which it is constituted, must be sufficiently small so that the flux resulting from the saturation of the core 3 by the coil S shall be incapable of de-magnetising the magnet 6 when the fluxes are in opposition.

ln the same way, if the excess currents are considered which create a flux additive to that of the magnet, there is also an advantage to be obtained in providing a core 3 of reduced cross-section so that the flux which saturatcs it cannot over-magnetise the magnet 6.

A high degree of accuracy of the points of operation necessitates, furthermore, a high degree of sensitivity of the relay and constancy over a long period of the elements which make up the relay, in spite of variations in temperature.

High sensitivity is obtained by the suppression or reduction of the parasitic air-gaps and the freedom of movement of the hinged members, the hinge action being obtained by the oscillation of a portion of the at moving armature on a sharp edge of the stationary yoke. in

L addition, the magnetic circuits are carefully joined, the connection between the core and the yoke 1 being effected by a conical coupling.

Constancy over a long period of the elements of the relay is obtained by the suppression of members which are likely to vary, either with time or as a function of the temperature, such as blade springs or coil springs, shafts having casual friction or the possibility of wear, etc. In fact, the armature 2 which is mechanically free, is only subjected to the combined action of the polarisation magnet 6, of the core 3 energized by the winding 8, and of the return magnet 9. As modern permanent magnets have a greater stability over a long period and as a function of the variations of temperature than springs, this arrangement ensures that the relay has accurate operational characteristics.

insensitivity to the action of gravity and to vibration is obtained by balancing the armature about its oscillating axis, the counter weight 2c which is necessary to achieve this balance serving, on the other hand, as a zone of attraction for the return magnet 9 and fulfilling by this` means a double purpose.

Finally, these arrangements provide the following advantages:

A high degree of sensitivity,

A high precision of the points of closure and of opening,

Rapid operation, either in closing or in opening, even with an energization which progressively increases or decreases,

Insensitivity to the force of gravity and to vibration,

Polarisation, that is to say sensitivity, to one direction only of continuous or rectified current,

Ability to withstand excess current in the direct sense which is only limited by its heating effect,

Ability to withstand excess current of almost any strength in the reverse direction without causing the relay to operate,

Negligible effect of direct or reverse excess currents on the following operation in respect of accuracy.

There is no relay at the present time which offers simultaneously the above series of advantages.

It will be quite clear that modifications may be made to the various forms of embodiment which have been described, in particular by the substitution of equivalent technical means without thereby departing from the spirit or the scope of the present invention.

What we claim is:

1. A polarized electromagnetic relay comprising a core, an electric circuit for energizing said core, a polarizing permanent magnet connected in series magnetic flow arrangement with said core to form therewith a closed magnetic circuit, a U-shaped yoke member connected with said magnet in parallel magnetic liow arrangement with said core, said yoke member having two branches extending on both sides of at least a part of said closed magnetic circuit, an armature pivoted at the end of one of said branches about an axis substantially perpendicular to the plane of said U-shaped member and extending opposite the end of the other of said branches, to form with said part of the closed magnetic circuit and said latter-mentioned branch two successive air-gaps, whereby said armature is subjected to the combined magnetic action of said closed magnetic circuit and said yoke member, and return means urging said armature away from said part and said latter-mentioned branch.

2. Relay as claimed in claim 1 wherein the core extends between the branches of the U-shaped yoke member, in the plane thereof, the permanent magnet extending outside said plane.

3. Relay as claimed in claim 1 further comprising a spacer member of non-magnetic material inserted into the closed magnetic circuit in series magnetic flow arrangement with the permanent magnet, before the point of References Cited in the le of this patent UNITED STATES PATENTS Wurts Oct. 27,

Scott Nov. 10,

Hoppe July 18,

Hall Jan. 11,

Plieger Dec. 25,

FOREIGN PATENTS Great Britain Aug. 12,

Great Bri-tain Aug. 15, 

